Developing an Explanation for Mouse Fur Color INTRODUCTION Rock pocket mice are interesting in many ways. They make a living in the intense heat of the desert. They also come in different fur colors, from tan to black. Scientists have a good understanding of what causes fur color in individual mice. The amount, type, and distribution of a pigment molecule called melanin gives fur its color. But why are almost all the mice in some populations black and those in other populations mostly tan? What determines these patterns?